WPP CEO Mark Read informed employees they have to return to the office four days a week from April.
The change to the global guidelines will apply across WPP's operations.
See the full timeline of advertising's new powerhouse merger here.
IPG posted 0% organic growth in Q3, trailing competitors like Publicis Groupe and Omnicom.
The rap star joined Publicis Groupe chairman and CEO Arthur Sadoun in annual 'Wishes' film.
The agency rebranded from MediaMonks to Monks in July.
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